<!--
 * @Descripttion: 
 * @Author: voanit
 * @Date: 2022-06-20 14:36:44
 * @LastEditors: voanit
 * @LastEditTime: 2022-06-20 14:44:45
-->
<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    * {
      padding: 0;
      margin: 0;
    }

    ul {
      display: flex;
      list-style: none;
      background-color: pink;
    }

    li:nth-child(1) {
      width: 100px;
    }

    li:nth-child(2n) {
      flex: 3;
      background-color: green;
    }

    li:nth-child(5) {
      flex: 4;
      background-color: green;
    }

    li:nth-child(3) {
      width: 100px;
    }
  </style>
</head>

<body>
  <ul>
    <li>1</li>
    <li>2</li>
    <li>3</li>
    <!-- <li>4</li>
    <li>5</li> -->
  </ul>

</body>

</html>